User:PesachZ/Road name inheritance

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Revision as of 19:39, 19 March 2015 by Qwaletee (talk | contribs) (Add examples, simplify some language, pose questions to be clarified, brief explanation of the effect on best continuation and wayfinders)

Unnamed segments (or no-name segments) are those segments where the None box has been ticked for the segment name. In routing instructions, they are often treated, for the current drive, as if they have the same name as the next named segment on the route. This is known as segment name inheritance. Any instruction for entering the segment will display and announce using the inherited name.

There are some situations where name inheritance does not apply, and the instruction is given without any name. The details of when inheritance occurs, and when it does not, are discussed at length in this article. The list of situations changed significantly in ((month)).

Unnamed segments also play a role in how Waze decides to create turn instructions, and, as a consequence, they may be used in creating wayfinders.

Current documentation

The USA wiki section for exit ramp names currently mentions in passing that segments with no name will use the next named segment in the route when they are announced in navigation.

If the exit off the main interstate or highway serves multiple exits further down the road, it may be advisable not to name the first exit ramp, but rather name only the ramps which are the first one to a distinct destination. The Waze client will give all the proper exit and keep left or right instructions to guide the driver to the correct exit, even if the first one is not named. That said, this should only be done if the signage for the first ramp is the same as that on the subsequent, named ramp.
Current basic understanding

Any segment which has the "None" box checked for its Name property can inherit the name of the next named segment in the route. If this segment is at a turn in your route where there would be a turn instruction, the inherited name is used in any instructions for the segment, as if the unnamed segment actually had that name.

For example given the following situation:

  • a highway exit
  • the exit is a single unnamed segment
  • the ramp connects in a "T" formation to a junction (three segments connect to the junction)
  • both of the other segments in the junction are named Frontage Way
  • Exit instruction: Exit to Frontage Way
  • Frontage Way is not the name of the segment. The instruction includes the name Frontage Way as if the segment did have the name, because it is inherited from the next segment

((((add small illustration)))

The name may be inherited from the next immediate segment in the route. If that segment is also unnamed, Waze will usually continue down the route until it finds a named segment to inherit. For example:

  • a highway exit
  • the ramp that forms the exit splits at the end, with the right side allowing a merge onto Frontage Way eastbound, and the left (ending at stop sign) allowing a left turn onto Frontage Way westbound
  • there are no other roads besides Frontage Way at the immediate end of the exit
  • there map has three segments in the exit to match the roadway configuration - the initial segment, and the two splits for left turn and right merge
  • all three exit segments are unnamed
  • Exit instructions:
  • For Frontage Way westbound (three instructions): Exit right to Frontage Way then keep left ... Keep left to Frontage Way then turn left ... Turn left to Frontage Way.
  • For Frontage Way eastbound (two instructions): Exit right to Frontage Way then keep right ... Keep right to Frontage Way. There will not be a third instruction, because this is a continuation (merges directly onto Frontage Way).

((((add small illustration)))

If remainder of the entire route is all unnamed segments, there is no name to inherit. The instruction will not give a name, and will only state the type of maneuver to make, e.g., the entire instruction might be "Turn left."

This can occur with destinations inside large parking lots. When none of the parking lot roads have names, there is no name to inherit for the turn into the lot.

The same will apply in situations where Waze does support inheritance (see [provide anchor link|below]). While there may be a named segment further along in the route, if Waze's rules prevent inheritance, there will be an instruction with no name.

It is important to understand that the inheritance looks along the route. In the previous example above, if the Frontage Way's name changes at the exit, and the westbound road is named Ander Way, then the instructions would be:

  • For routes to Frontage Way westbound: Exit right to Ander Way then keep left ... Keep left to Ander Way then turn left ... Turn left to Ander Way.
  • For routes to Frontage Way eastbound: Exit right to Frontage Way then keep right ... Keep right to Frontage Way.

((((add two small illustrations, showing the two routes)))

Recent changes

As of The status-quo above still applies, and the following new changes do not affect  Freeways  or  Ramps .

For all other road types there are now two things which can prevent inheritance of the next named segment in the route. Either one of the following will cause Waze to not attempt inheritance:

  1. Waze will not attempt inheritance past 400 meters (1312 feet) of unnamed segment
  2. Waze will not attempt to look at more than four unnamed segments (current segments plus next three on route) to find a name to inherit

If the situation meets either or both of the criteria above, you will just get the turn instruction without a street name displayed or spoken over TTS.

The 400 meters can all be in the initial segment, or it can be a combination of several segments. Once the total unnamed length reaches 400, Waze does not attempt to look for a named segment to inherit. This means that any unnamed segment (besides freeway or ramp types) that is 400m or more, will never inherit a name. For segments of less than 400m, Waze will attempt to look at at least one more segment. But if that next segment is unnamed, and the total of length the first and second segments is over 400m (e.g., 150m and 251m)

Remember these new changes do not apply to Freeways or ramps, a freeway or ramp interchange can have as many consecutive no-name segments as you'd like, and be as long as you'd like, and they will still all inherit the next name on your route. There is no known maximum length or maximum number fo segments to be examined, through the end of the route

(((Open questions:

  • is it MORE than 400m, or is it 400m OR MORE?
  • If the initial segment is 500m of ramp, followed by two very short unnamed street segments, followed by a named street segment, will it inherit because the initial segment is ramp, or will it stop because 400m was exceeded? If it does not stop, what if the first street segment is also 500m, so there is now >400m of non-ramp?
  • Vice versa: if the initial segment is 100m MH, followed by 300m unnamed ramp, followed by a named segment, does it stop after 500m because the initial segment is MH? Or does the ramp's 500m always get ignored for the inheritance blocking?

-answers TBD)))

Best continuation and wayfinders

This section covers several advanced topics. They are complex, and have several articles fully dedicated to the subject. They are covered here in brief, for a high level understanding of how unnamed segments fit into these subjects. Links are provided to teh main subject articles.

Waze does not provide an instruction for all segments in a route. When a segment is considered a continuation of the previous segment, Waze does not need to instruct the driver. For example, there is no instruction when crossing through a standard four-way, right-angle intersection, nor for driving past an exit on a highway, without taking the exit.

The details of when Waze gives an instruction or not are complex, and covered in this article. Part of the consideration is whether the two segments have the same name. When the names are the same, Waze is more likely to consider it a non-instruction continuation; when they are different, Waze is more likely to consider the need for an instruction.

For the purposes of continuations, Waze does not use inheritance. Given the following situation:

  • A segment route named Best Circle
  • Followed immediately by an unnamed segment
  • Followed immediately by another segment named Best Circle

Waze, when evaluating whether or not to give any instruction, will consider the middle segment to have a different name than the other two (Best Circle, BLANK, Best Circle). It will not allow the middle segment to inherit the name of the third segment.

However, if Waze decides that an instruction is required to from from the first to the second segment, when Waze generates that instruction, it will inherit the third segment's name, and issue an instruction like "Keep left to Best Circle."

To fully understand whether Waze will generate an instruction or not, including the application of transitions to or from an unnamed road, please carefully study How Waze determines turn / keep / exit maneuvers.

This affects wayfinders. A wayfinder is used to force an instruction where Waze would normally not issue any instruction. To force an instruction, part of the technique involves making sure that two segments on a route will have different names. If one segment is named and the other is unnamed, that will meet the criteria for having different names.

To fully understand how wayfinders work, and carefully study the wayfinder section of the Junction Style Guide.